The present invention relates generally to systems for controlling exhaust emissions produced by an internal combustion engine, and more specifically to systems operable to control exhaust emissions by prescribing maximum allowable emission levels to be produced by the engine and further to such systems including Auxiliary Emission Control Device (AECD) accommodation.
Systems for controlling exhaust emissions produced by an internal combustion engine are known and have been widely implemented, particularly in the heavy-duty diesel engine industry. Historically, the Environmental Protection Agency (EPA) has promulgated limits for allowable levels of certain exhaust emissions such oxides of nitrogen (NOx). However, such emission level requirements promulgated by the EPA are typically subject to frequent changes that are often difficult to integrate into existing engine control logic.
The EPA has recently provided for the possibility of allowing engine behavior that deviates from xe2x80x9cnormalxe2x80x9d or expected engine operation while meeting emission requirements through the use of one or more auxiliary emission control devices or AECDs, wherein an AECD is defined for purposes of the subject invention as a software structure that defines, as a function of one or more engine operating parameters, a current operational state of the engine. As an example, a particular AECD may define an engine speed AECD responsive to at least a signal produced by an engine speed sensor to produce one or more control outputs. It is to be understood that this example is provided only by way of illustration and is not necessarily indicative of a practical AECD. In any case, the use of any one or more AECDs with a particular engine configuration is, at present, privately negotiated with the EPA by the individual engine manufacturer, and the number as well as the functions of the one or more permitted AECDs are accordingly considered by the various engine manufacturers to be highly confidential. Like emission requirements, AECD definitions permitted by the EPA are also subject to frequent changes, wherein assimilation of newly permitted AECDs as well as abandonment of, or changes to, existing AECDs are likewise difficult to implement into known engine control routines.
One drawback associated with known systems for implementing EPA-mandated emission requirements as well as negotiated AECD definitions is that there typically exists an interdependency between the emissions/AECD logic and the base engine control routines. What is therefore needed is a system that isolates emission requirements/allowances from base engine control logic. Such a system should be easily adaptable to changing emission requirements and/or AECD definitions and sufficiently flexible to accommodate any number of AECDs.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for controlling exhaust emissions produced by an internal combustion engine comprises an engine speed sensor sensing a rotational speed of an internal combustion engine and producing a speed signal corresponding thereto, means for determining an altitude of said engine and producing an altitude value corresponding thereto, means for determining an ambient temperature external to said engine and producing a temperature value corresponding thereto, means for determining an output torque produced by said engine and producing a torque value corresponding thereto, and a control computer determining a maximum allowable emission level as a function of said speed signal, said altitude value, said temperature value and said torque value, said computer controlling an air handling system of said engine as a function of said maximum allowable emission level such that exhaust emissions produced by said engine are limited to said maximum allowable emission level.
In accordance with another aspect of the present invention, a method of controlling exhaust emissions produced by an internal combustion engine comprises determining a rotational speed of an internal combustion engine, determining an altitude of said engine, determining an ambient temperature external to said engine, determining an output torque produced by said engine, determining a maximum allowable emission level as a function of said rotational speed, said altitude, said ambient temperature and said output torque, and controlling an air handling system of said engine as a function of said maximum allowable emission level such that exhaust emissions produced by said engine are limited to said maximum allowable emission level.
In accordance with a further aspect of the present invention, a system for controlling exhaust emissions produced by an internal combustion engine comprises means for determining a first operating parameter of an internal combustion engine and producing a first operating parameter value corresponding thereto, a first auxiliary emission control device (AECD) producing a first emission level as a function of at least said first operating parameter value, and a control computer determining a maximum allowable emission level as a function of said first emission level and a reference emission level, said computer controlling an air handling system of said engine as a function of said maximum allowable emission level such that exhaust emissions produced by said engine are limited to said maximum allowable emission level.
In accordance with yet another aspect of the present invention, a system for controlling exhaust emissions produced by an internal combustion engine comprises a plurality of means for determining a corresponding plurality of different operating parameters of an internal combustion engine and producing a corresponding plurality of operating parameter values corresponding thereto, a number of auxiliary emission control devices (AECDs) each producing an independent emission level as a function of at least one of any of said plurality of operating parameter values, and a control computer determining a maximum allowable emission level as a maximum one of a reference emission level and each of said emission levels produced by said number of AECDs, said computer controlling an air handling system of said engine as a function of said maximum allowable emission level such that exhaust emissions produced by said engine are limited to said maximum allowable emission level.
In accordance with still another aspect of the present invention, a method of controlling exhaust emissions produced by an internal combustion engine comprises determining a plurality of operating parameters each corresponding to a different operating condition of an internal combustion engine, determining a number of emission levels each corresponding to a different auxiliary emission control device (AECD) and each as a function of at least one of any of said plurality of operating parameters, determining a maximum allowable emission level as a maximum one of a reference emission level and said number of emission levels, and controlling an air handling system of said engine as a function of said maximum allowable emission level such that exhaust emissions produced by said engine are limited to said maximum allowable emission level.
In accordance with still a further aspect of the present invention, a system for controlling exhaust emissions produced by an internal combustion engine comprises means for determining a first operating parameter of an internal combustion engine and producing a first operating parameter value corresponding thereto, a first auxiliary emission control device (AECD) producing a first state value indicative of a first operating condition of said engine as a function of at least said first operating parameter value, and a control computer controlling exhaust emissions produced by said engine by controlling an air handling system of said engine as a function of said first state value.
In accordance with yet another aspect of the present invention, a system for controlling exhaust emissions produced by an internal combustion engine comprises a plurality of means for determining a corresponding plurality of different operating parameters of an internal combustion engine and producing a corresponding plurality of operating parameter values corresponding thereto, a number of auxiliary emission control devices (AECDs) producing a corresponding number of independent state values each as a function of at least one of any of said plurality of operating parameter values, and a control computer controlling exhaust emissions produced by said engine by controlling an air handling system of said engine as a function of said number of state values.
In accordance with still a further aspect of the present invention, a method of controlling exhaust emissions produced by an internal combustion engine comprises determining a plurality of operating parameters each corresponding to a different operating condition of an internal combustion engine, determining a number of state values each corresponding to a different auxiliary emission control device (AECD) and each as a function of at least one of any of said plurality of operating parameters, and controlling exhaust emissions produced by said engine by controlling an air handling system of said engine as a function of said first state value.
One object of the present invention is to provide a system for controlling exhaust emissions produced by an internal combustion engine by prescribing a maximum allowable emission level and controlling an air handling system of the engine to limit exhaust emissions produced by the engine to the maximum allowable emission level.
Another object of the present invention is to provide such a system that further accommodates any number of auxiliary emission control devices (AECDs).
A further object of the present invention is to provide such a system that determines the maximum allowable emission level as a maximum one of a reference emission level and any number of auxiliary emission levels associated with any corresponding number of AECDs.
Still another object of the present invention is to provide such a system responsive to the operational states of one or more of the AECDs to take action in addition to maintaining exhaust emissions below the maximum allowable emission level in order to achieve a desired engine operational goal such as, for example, lowering turbocharger turbine speed, lowering EGR system heat rejection, increasing fuel economy, and the like.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiments.